CN114940500B - Fly ash-based NaP type molecular sieve and preparation method and application thereof - Google Patents
Fly ash-based NaP type molecular sieve and preparation method and application thereof Download PDFInfo
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Abstract
The invention belongs to the technical field of coal-based solid waste. The invention provides a fly ash-based NaP type molecular sieve, and a preparation method and application thereof. The method comprises the steps of mixing fly ash with acid liquor for acid washing to obtain acid-washed fly ash; mixing the acid-washed fly ash, sodium hydroxide and water, and then activating by utilizing microwave radiation, and fully carrying out a melting reaction at high temperature to convert the silicon aluminum mineral substances which are not easy to dissolve into aluminosilicate; then accelerating the intense movement of molecules under the cavitation of ultrasound, pre-crystallizing by utilizing ultrasound, shortening the time of inducing nucleation, fully carrying out internal reaction of the mixed solution, increasing mass transfer rate, accelerating the formation of more soluble and very tiny silica-alumina gel particles, thereby obtaining the fly ash-based NaP type molecular sieve with high purity and uniform particle size. The preparation method provided by the invention has the advantages of simple process and low requirement, saves a large amount of industrial raw materials, improves the utilization rate of the fly ash, promotes the utilization of the high added value of the fly ash, and reduces the pollution of the fly ash to the environment.
Description
Technical Field
The invention relates to the technical field of coal-based solid waste, in particular to a fly ash-based NaP type molecular sieve, a preparation method and application thereof.
Background
Coal drives the rapid development of industry, but a large amount of industrial solid waste fly ash is generated while coal is combusted. Fly ash is one of the main solid wastes in industry, and a large amount of accumulation has serious threat and harm to the resource environment and human health. Therefore, the reasonable and efficient conversion of the fly ash into the material with the resource and high added value has important practical significance.
The fly ash contains a large amount of SiO 2 、Al 2 O 3 The components (the content is about 50% -80%) also contain Fe 2 O 3 、Na 2 O, caO, cuO, etc. The fly ash is an amorphous porous material, and the molecular sieve is an inorganic aluminosilicate crystal, and the two crystals only have larger difference in crystal structure, so that feasibility is provided for preparing the fly ash-based molecular sieve from the fly ash. The utilization of the raw materials of the fly ash is low in cost, waste can be changed into valuable, the fly ash can be effectively utilized to realize the maximum utilization of the value, and the two-way development of economic benefit and environmental benefit is realized.
At present, the preparation of the fly ash-based NaP molecular sieve is in a laboratory research stage, and the research and related reports of preparing the NaP molecular sieve by taking the fly ash as a raw material are few. NaP molecular sieve is a hydrated crystalline aluminosilicate, has three-dimensional network structure of infinitely extended silicon aluminum tetrahedron, and is prepared from [ SiO 4 ] 4- Tetrahedra and [ AlO ] 4 ] 5- Tetrahedra form a three-dimensional framework structure in different arrangements by sharing oxygen atoms. The basic structural unit is [ SiO ] 4 ] 4- Tetrahedra and [ AlO ] 4 ] 5- The eight-membered ring formed by tetrahedra forms more regular holes and pore channels, and the NaP type molecular sieve has smaller pore size, has a unique eight-membered ring two-dimensional pore channel rhombic calcium (GIS) framework topological structure, is different from the common X, Y type and other fly ash-based molecular sieves, and has good development prospect in the adsorption field and the ion exchange field.
In the prior literature, liu and other fly ash are used for removing impurities through acid washing, a hydrothermal condition is adopted for preparing a P-type molecular sieve, and finally the optimized specific surface area is 42m 2 And/g, pore diameter is 6nm. (LiuY, luo Q, wang G, et al Synthesis and characterization of zeolite from coal fly ash [ J)]Materials Research Express,2018,5 (5): 055507.) Meng et al use epidesmine as the silicon source and use hydrothermal method to control SiO 2 And Al 2 O 3 Molar ratio, synthesizing NaP zeolite, experimental result shows that in SiO 2 /Al 2 O 3 And H 2 O/Na 2 Under O condition, naP zeolite with high quality can be obtained. BET surface area and total surface area of 17.1359m 2 。(Meng X,Guo X,ZhongY,et al.Synthesis of a high-quality NaP zeolite from epidesmine by a hydrothermal method[J]Bulletin of Materials Science,2019,42 (5): 1-8.). However, these process techniques have the disadvantages of easy deposition of molecular sieve precursors at the bottom of the reaction kettle, aggregation during the growth of crystal nuclei, poor inter-phase mass transfer efficiency, long synthesis time, high cost and the like.
In the traditional method for preparing the molecular sieve by using the fly ash, the alkali-melting hydrothermal method can fully activate the active ingredients in the fly ash, and different types of zeolite molecular sieve products can be obtained by adjusting the silicon-aluminum ratio, but the hydrothermal synthesis method requires longer time, has large energy consumption, has poor inter-phase mass transfer efficiency when a precursor is nucleated, and is not easy to form a molecular sieve with a better crystal form. The microwave-ultrasonic auxiliary synthesis method not only can shorten the activation time and fully release inert components in the fly ash to provide sufficient silicon source and aluminum source, but also has a series of advantages of reducing energy consumption, reducing production cost, high preparation efficiency, good crystal form of the molecular sieve and the like. The Chinese patent with the publication number of CN201611233693.4 discloses a microwave preparation method of a P-type molecular sieve, which synthesizes a P-type zeolite product by adopting a microwave method, wherein the method is to uniformly mix tetraethoxysilane, sodium hydroxide and water according to a certain molar ratio to obtain a mixture A; uniformly mixing sodium metaaluminate, sodium hydroxide and water according to a certain molar ratio to obtain a mixture B; gradually adding the mixture B into the mixture A and uniformly stirring at 60 ℃ for 1h to obtain a P-type molecular sieve mother solution; transferring the P-type molecular sieve mother liquor into a microwave reaction kettle, crystallizing for 3 hours at 100 ℃ for the first time by adopting a microwave heating mode, crystallizing for 3 hours at 180 ℃ for the second time, filtering a solid product obtained by crystallization, washing with water and ethanol for a plurality of times until the pH value is close to neutral, and drying for 3 hours at 100 ℃ to obtain the P-type molecular sieve. The method has high purity, but the preparation process is complicated, and in addition, the consumed raw materials are obtained by a purification method on the basis, so that the cost is increased, secondary pollution is easy to generate, and the industrial production trend is not easy to realize. The pre-crystallization process is used as a key process for preparing the fly ash-based NaP molecular sieve precursor liquid, and is related to nucleation and molecular sieve grain size. Therefore, how to provide a method for preparing NaP type molecular sieve by using fly ash as raw material is a problem to be solved.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a fly ash-based NaP type molecular sieve, and a preparation method and application thereof.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a preparation method of a fly ash-based NaP type molecular sieve, which comprises the following steps:
(1) Mixing the fly ash with acid liquor and drying to obtain acid-washed fly ash;
(2) Mixing the acid-washed fly ash, sodium hydroxide and water, and then calcining by microwaves to obtain activated fly ash;
(3) And mixing the activated fly ash with water, and sequentially carrying out ultrasonic treatment, crystallization and drying to obtain the fly ash-based NaP molecular sieve.
Preferably, the acid liquor in the step (1) is hydrochloric acid solution or nitric acid solution, and the concentration of the acid liquor is 1-3 mol/L;
the mass ratio of the fly ash to the acid liquid is 1:2 to 6.
Preferably, the stirring speed of the mixing in the step (1) is 50-100 rpm, the stirring time is 24-26 h, and the stirring temperature is 20-30 ℃;
the temperature of the drying in the step (1) is 100-110 ℃ and the time is 12-13 h.
Preferably, in the step (2), the mass ratio of the acid-washed fly ash to the sodium hydroxide is 1:0.5 to 2;
the concentration of sodium hydroxide in the mixture of the acid-washed fly ash, sodium hydroxide and water is 1.25-3.75 mol/L.
Preferably, the temperature of the microwave calcination in the step (2) is 700-800 ℃, the time is 1-2 h, and the frequency is 30-35 kHz.
Preferably, in the step (3), the mass volume ratio of the activated fly ash to the water is 1g: 2-4 mL.
Preferably, the ultrasonic frequency in the step (3) is 30-35 kHz, the temperature is 50-60 ℃ and the time is 1-4 hours;
the crystallization temperature is 100-110 ℃ and the crystallization time is 12-48 h.
Preferably, in the step (3), the drying temperature is 105-115 ℃, the vacuum degree is-40 to-80 KPa, and the time is 12-13 h.
The invention also provides the fly ash-based NaP type molecular sieve obtained by the preparation method.
The invention also provides application of the fly ash-based NaP type molecular sieve in carbon dioxide adsorption.
The invention provides a preparation method of a fly ash-based NaP type molecular sieve. The NaP type molecular sieve is prepared by taking fly ash as a raw material and adopting a microwave-ultrasonic auxiliary method. The method comprises the steps of mixing fly ash with acid liquor for acid washing to obtain acid-washed fly ash; mixing the acid-washed fly ash, sodium hydroxide and water, and then activating by utilizing microwave radiation, and fully carrying out a melting reaction at high temperature to convert the silicon aluminum mineral substances which are not easy to dissolve into aluminosilicate; then accelerating the intense movement of molecules under the cavitation of ultrasound, pre-crystallizing by utilizing ultrasound, shortening the time of inducing nucleation, fully carrying out internal reaction of the mixed solution, increasing mass transfer rate, accelerating the formation of more soluble and very tiny silica-alumina gel particles, thereby obtaining the fly ash-based NaP type molecular sieve with high purity and uniform particle size.
The preparation method provided by the invention has the advantages of simple process, low requirement, easiness in operation and low cost, and the fly ash is used as a raw material to prepare the fly ash-based NaP type molecular sieve, so that the raw material cost is low, a large amount of industrial raw materials are saved, chemical agents or purification is not needed, the utilization rate of the fly ash can be improved, the high added value utilization of the fly ash is promoted, and the pollution of the fly ash to the environment is reduced.
The fly ash based NaP type molecular sieve provided by the invention has wide application field and can be applied toThe prepared fly ash-based NaP type molecular sieve is used in the fields of ion exchange, catalysis, adsorption and the like, and has better CO adsorption 2 Provides a way for the high-value recycling comprehensive utilization of the fly ash.
Drawings
FIG. 1 is an X-ray diffraction pattern of the NaP type molecular sieve of example 1;
FIG. 2 is an electron Scanning Electron Microscope (SEM) image of NaP-type molecular sieve of example 1;
FIG. 3 is a graph showing the Na element distribution of the NaP-type molecular sieve of example 1;
FIG. 4 is a Si element distribution spectrum of the NaP type molecular sieve in example 1;
FIG. 5 is an Al element distribution spectrum of the NaP type molecular sieve in example 1;
FIG. 6 is an O-element distribution energy spectrum of NaP type molecular sieve in example 1;
FIG. 7 is an infrared spectrum of NaP type molecular sieve in example 1;
FIG. 8 is a graph of the thermal stability of NaP type molecular sieves of example 1;
FIG. 9 is a graph of adsorbed carbon dioxide for the NaP type molecular sieve of example 1.
Detailed Description
The invention provides a preparation method of a fly ash-based NaP type molecular sieve, which comprises the following steps:
(1) Mixing the fly ash with acid liquor and drying to obtain acid-washed fly ash;
(2) Mixing the acid-washed fly ash, sodium hydroxide and water, and then calcining by microwaves to obtain activated fly ash;
(3) And mixing the activated fly ash with water, and sequentially carrying out ultrasonic treatment, crystallization and drying to obtain the fly ash-based NaP molecular sieve.
In the present invention, siO in fly ash 2 And Al 2 O 3 The mass fraction of the mass sum is preferably 80% or more, more preferably 82% or more, and still more preferably 84% or more; the molar ratio of the silicon element to the aluminum element is preferably 3.4 to 5.6:1, more preferably 3.8 to 5.2:1, more preferably 4.2 to 4.8:1.
in the present invention, the pulverized fuel ash is refined and then mixed with an acid solution, and the mesh number of the refined screen is preferably 200 mesh or more, more preferably 300 mesh or more, and still more preferably 400 mesh or more.
In the present invention, the acid solution in the step (1) is preferably a hydrochloric acid solution or a nitric acid solution, and the concentration of the acid solution is preferably 1 to 3mol/L, more preferably 1.5 to 2.5mol/L, and still more preferably 1.8 to 2.2mol/L.
In the invention, the mass ratio of the fly ash to the acid liquor is preferably 1:2 to 6, more preferably 1:3 to 5, more preferably 1:3.5 to 4.5.
In the present invention, the stirring speed of the mixing in the step (1) is preferably 50 to 100rpm, more preferably 60 to 90rpm, still more preferably 70 to 80rpm; the stirring time is preferably 24 to 26 hours, more preferably 24.5 to 25.5 hours, and still more preferably 24.8 to 25.2 hours; the stirring temperature is preferably 20 to 30 ℃, more preferably 22 to 28 ℃, still more preferably 24 to 26 ℃.
In the invention, after stirring, the fly ash solution is filtered, washed to be neutral and then dried in the next step.
In the present invention, the temperature of the drying in the step (1) is preferably 100 to 110 ℃, more preferably 102 to 108 ℃, still more preferably 104 to 106 ℃; the time is preferably 12 to 13 hours, more preferably 12.2 to 12.8 hours, and still more preferably 12.4 to 12.6 hours.
In the present invention, the mass ratio of the acid-washed fly ash to the sodium hydroxide in the step (2) is preferably 1:0.5 to 2, more preferably 1:1 to 1.5, more preferably 1:1.2 to 1.3.
In the present invention, the concentration of sodium hydroxide in the mixture obtained by mixing the acid-washed fly ash, sodium hydroxide and water is preferably 1.25 to 3.75mol/L, more preferably 2 to 3mol/L, and still more preferably 2.4 to 2.6mol/L.
In the invention, the acid-washed fly ash, sodium hydroxide and water are mixed and stirred uniformly, and then the next microwave calcination is carried out.
In the invention, the wave absorber is added before microwave calcination, so that the reaction is more sufficient; the mass ratio of the wave absorber to the fly ash is preferably 1:1.5 to 2.5, more preferably 1:1.6 to 2.4, more preferably 1:1.8 to 2.2; the wave absorber is preferably SiC.
In the present invention, the temperature of the microwave calcination in the step (2) is preferably 700 to 800 ℃, more preferably 720 to 780 ℃, still more preferably 740 to 760 ℃; the time is preferably 1 to 2 hours, more preferably 1.2 to 1.8 hours, still more preferably 1.4 to 1.6 hours, and the frequency is preferably 30 to 35kHz, still more preferably 31 to 34kHz, still more preferably 32 to 33kHz.
In the invention, after the microwave calcination is finished, the calcined product is naturally cooled, and the target temperature of natural cooling is preferably 20-30 ℃, more preferably 22-28 ℃, and even more preferably 24-26 ℃; and cooling to obtain the activated fly ash.
In the present invention, the mass to volume ratio of the activated fly ash to water in step (3) is preferably 1g:2 to 4mL, more preferably 1g:2.5 to 3.5mL, more preferably 1g: 2.8-3.2 mL.
In the present invention, the frequency of the ultrasonic waves in the step (3) is preferably 30 to 35kHz, more preferably 31 to 34kHz, still more preferably 32 to 33kHz; the temperature is preferably 50 to 60 ℃, more preferably 52 to 58 ℃, still more preferably 54 to 56 ℃; the time is preferably 1 to4 hours, more preferably 2 to 3 hours, and still more preferably 2.4 to 2.6 hours.
In the present invention, the crystallization temperature is preferably 100 to 110 ℃, more preferably 102 to 108 ℃, and even more preferably 104 to 106 ℃; the time is preferably 12 to 48 hours, more preferably 20 to 40 hours, and even more preferably 25 to 35 hours.
In the present invention, the temperature of the drying in the step (3) is preferably 105 to 115 ℃, more preferably 106 to 114 ℃, still more preferably 108 to 112 ℃; the vacuum degree is preferably-40 to-80 KPa, more preferably-50 to-70 KPa, more preferably-55 to-65 KPa; the time is preferably 12 to 13 hours, more preferably 12.2 to 12.8 hours, and still more preferably 12.4 to 12.6 hours.
In the present invention, the fine screen mesh is preferably 200 mesh or more, more preferably 300 mesh or more, and still more preferably 400 mesh or more after the drying is completed.
The invention also provides the fly ash-based NaP type molecular sieve obtained by the preparation method.
The invention also provides application of the fly ash-based NaP type molecular sieve in carbon dioxide adsorption.
The technical solutions provided by the present invention are described in detail below with reference to examples, but they should not be construed as limiting the scope of the present invention.
Example 1
Fly ash (SiO) 2 And Al 2 O 3 The mass fraction of the sum is 85%, and the mole ratio of silicon element to aluminum element is 3.8: 1) Grinding into fine powder, and sieving with 200 mesh sieve; mixing 200g of fly ash with 800g of hydrochloric acid with the concentration of 2mol/L, stirring at 25 ℃ and 80rpm for 25 hours, filtering the fly ash solution after stirring, washing to be neutral, and drying at 105 ℃ for 12 hours to obtain the acid-washed fly ash.
The mass ratio of the acid-washed fly ash to the sodium hydroxide is controlled to be 1:2, mixing the acid-washed fly ash, sodium hydroxide and water, wherein the concentration of the sodium hydroxide in the mixture is 1.65mol/L; after stirring well, the mixture was poured into a reactor made of quartz. Then the quartz reactor with the mixture is put on a rotary workbench of an industrial microwave heating device, 100g of SiC is added as a wave absorber, the mixture is calcined for 1h at 700 ℃ and 32kHz, and the mixture is taken out and naturally cooled to 25 ℃ for standby.
Activated fly ash and water were mixed in an amount of 1g: mixing at a ratio of 4mL, performing ultrasonic treatment at 35kHz and 55 ℃ for 2h, crystallizing at 100 ℃ for 48h, filtering the crystallized product by using a Buchner funnel, and drying at 110 ℃ and 60KPa for 12h; and after the drying is finished, passing through a 200-target quasi-test sieve to obtain the NaP type molecular sieve.
In this example, the yield of the fly ash-based NaP-type molecular sieve was 88%.
The result of X-ray diffraction of the molecular sieve prepared in this example is shown in fig. 1, and it can be seen from the graph that under the detection of X-ray diffraction, the fly ash-based NaP-type molecular sieve prepared in this example has obvious characteristic peaks, and the angles of 2θ thereof are respectively: 12.4 degrees, 17.7 degrees, 21.6 degrees, 28.1 degrees, 33.4 degrees, 35.6 degrees, 38.1 degrees, 44.1 degrees and 46.1 degrees are consistent with peak positions of standard cards (NaP molecular sieves), are consistent with peak positions of characteristic peaks of NaP molecular sieves reported in literature, are consistent with peak positions of NaP molecular sieves, have single crystal phases, and have high purity.
The molecular sieve prepared in this example is electronically scanned, and the obtained electron microscope image is shown in fig. 2, and it can be seen from the image that the morphology of the fly ash-based NaP molecular sieve synthesized in this example is spherical and aggregate-like, the surface has a thread shape, the morphology is complete, the dispersibility is good, the edges and corners are clear, the particle size is uniform, the average particle size is 1.6um, and the proportion of the particle size in the range is more than 85%.
The molecular sieve prepared in this embodiment is subjected to element distribution energy spectrum detection, the Na element distribution energy spectrum is shown in fig. 3, the Si element distribution energy spectrum is shown in fig. 4, the Al element distribution energy spectrum is shown in fig. 5, and the O element distribution energy spectrum is shown in fig. 6. It can be seen from fig. 3 to fig. 6 that the molecular sieve contains Na, si, al, O element, and the positions of the elements are the same, which indicates that each NaP type molecular sieve grain is composed of Na, si, al, O elements, and accords with the element characteristics of the NaP type molecular sieve composition, i.e., the prepared molecular sieve product is a NaP type molecular sieve.
The molecular sieve prepared in the embodiment is subjected to infrared spectrum detection, the infrared spectrum is shown in figure 7, and the result shows that in the product fly ash-based NaP molecular sieve, the molecular sieve is 3480cm -1 The wider absorption peak at the position is an expansion vibration peak of 1655cm for adsorbing the-OH group on the water surface of the molecular sieve -1 The absorption peak at the position is-OH bending vibration peak of adsorbed water, 990cm -1 The absorption peak at the position is asymmetric stretching vibration of TO4 (T=Si, al) tetrahedron in the molecular sieve, 742cm -1 And 680cm -1 The absorption peaks appearing at the positions are Si-O tetrahedron symmetrical telescopic vibration absorption peak and asymmetrical telescopic vibration absorption peak, 604cm -1 The absorption peak at the position is a double-ring vibration absorption peak connected with the outside of the molecular sieve, which shows that the crystal framework of the molecular sieve is of a double-ring structure. 440cm -1 The absorption peak appearing at the position is NaP molecular sieveIs due to the bending vibration peak of T-O. The prepared fly ash-based NaP type molecular sieve product accords with the measurement area of the molecular sieve and the framework vibration band characteristics of the molecular sieve, and further shows that the molecular sieve product prepared by the embodiment is the NaP type molecular sieve.
The molecular sieve prepared in this example was subjected to thermogravimetric analysis, and the thermal stability graph is shown in fig. 8, from which it can be seen that the mass loss rate of the fly ash-based NaP molecular sieve before 200 ℃ is 7.8%, which is mainly attributed to the vaporization of the molecular sieve free adsorbed water. The mass loss is 3.4% over this temperature range of 200-480 c, which is mainly due to the vaporization of the molecular sieve adsorbed water and the structurally coordinated water. After 480 ℃, the mass loss was essentially unchanged. The exothermic peak appears at 690 ℃ in the fly ash-based NaP molecular sieve according to the differential thermal curve, the weight is basically unchanged, and the energy change is larger, which indicates that the prepared fly ash-based NaP undergoes crystal transformation at the temperature, and the energy change caused by the release of lattice energy due to structural collapse is larger. The mass loss rate of the fly ash-based NaP molecular sieve is 11.2% on the whole, and the mass loss is small. The use temperature of the commercial molecular sieve is below 700 ℃, and the prepared fly ash-based NaP molecular sieve has good thermal stability.
The molecular sieve prepared in this example was subjected to carbon dioxide adsorption experiments, and the results are shown in FIG. 9, in which NaP molecular sieve adsorbs CO 2 Can be up to 118cm 3 Per gram, has better CO 2 Adsorption performance.
Example 2
Fly ash (SiO) 2 And Al 2 O 3 The mass fraction of the mass sum is 84%, and the mole ratio of silicon element to aluminum element is 5.5: 1) Grinding into fine powder, and sieving with 300 mesh sieve; mixing 100g of fly ash with 200g of nitric acid solution with the concentration of 1.5mol/L, stirring for 26 hours at 20 ℃ and 80rpm, carrying out suction filtration on the fly ash solution after stirring, washing to be neutral, and drying for 13 hours at 110 ℃ to obtain the acid-washed fly ash.
The mass ratio of the acid-washed fly ash to the sodium hydroxide is controlled to be 1:1.5, mixing the acid-washed fly ash, sodium hydroxide and water, wherein the concentration of the sodium hydroxide in the mixture is 3.25mol/L; after stirring well, the mixture was poured into a reactor made of quartz. Then the quartz reactor with the mixture is placed on a rotary workbench of an industrial microwave heating device, 40g of SiC is added as a wave absorber, the mixture is calcined for 2 hours at 730 ℃ and 30kHz, and the mixture is taken out and naturally cooled to 30 ℃ for standby.
Activated fly ash and water were mixed in an amount of 1g: mixing at a ratio of 2mL, performing ultrasonic treatment at 30kHz and 50 ℃ for 3h, crystallizing at 110 ℃ for 36h, filtering the crystallized product by using a Buchner funnel, and drying at 115 ℃ and 40KPa for 13h; and after the drying is finished, passing through a 300-target quasi-test sieve to obtain the NaP type molecular sieve.
In this example, the yield of the fly ash-based NaP-type molecular sieve was 86%, and CO was adsorbed 2 Can reach 117.5cm 3 /g。
Example 3
Fly ash (SiO) 2 And Al 2 O 3 The mass fraction of the sum is 90%, and the mole ratio of silicon element to aluminum element is 4: 1) Grinding into fine powder, and sieving with 200 mesh sieve; mixing 200g of fly ash with 1000g of hydrochloric acid solution with the concentration of 2.3mol/L, stirring for 24 hours at the temperature of 23 ℃ and the rotation speed of 100rpm, carrying out suction filtration on the fly ash solution after stirring, washing to be neutral, and drying for 12 hours at the temperature of 105 ℃ to obtain the acid-washed fly ash.
The mass ratio of the acid-washed fly ash to the sodium hydroxide is controlled to be 1:0.8, mixing the acid-washed fly ash, sodium hydroxide and water, wherein the concentration of the sodium hydroxide in the mixture is 1.5mol/L; after stirring well, the mixture was poured into a reactor made of quartz. Then the quartz reactor with the mixture is placed on a rotary workbench of an industrial microwave heating device, 100g of SiC is added as a wave absorber, the mixture is calcined for 1.5 hours at 780 ℃ and 34kHz, and the mixture is taken out and naturally cooled to 25 ℃ for standby.
Activated fly ash and water were mixed in an amount of 1g:3.8mL, ultrasonic treating at 35kHz and 60 deg.C for 2h, crystallizing at 105 deg.C for 40h, filtering the crystallized product with Buchner funnel, and drying at 110 deg.C and-50 KPa for 12h; and after the drying is finished, passing through a 200-target quasi-test sieve to obtain the NaP type molecular sieve.
In this example, fly ash baseNaP molecular sieve has 88% of yield and can adsorb CO 2 Can reach a quantity of 115.3cm 3 /g。
Example 4
Fly ash (SiO) 2 And Al 2 O 3 The mass fraction of the mass sum is 88%, and the mole ratio of silicon element to aluminum element is 5.2: 1) Grinding into fine powder, and sieving with 400 mesh sieve; mixing 300g of fly ash and 1800g of nitric acid solution with the concentration of 1.6mol/L, stirring at 30 ℃ and 75rpm for 25 hours, carrying out suction filtration on the fly ash solution after stirring, washing to be neutral, and drying at 110 ℃ for 13 hours to obtain the acid-washed fly ash.
The mass ratio of the acid-washed fly ash to the sodium hydroxide is controlled to be 1:1.8, mixing the acid-washed fly ash, sodium hydroxide and water, wherein the concentration of the sodium hydroxide in the mixture is 3.6mol/L; after stirring well, the mixture was poured into a reactor made of quartz. Then the quartz reactor with the mixture is placed on a rotary workbench of an industrial microwave heating device, 150g of SiC is added as a wave absorber, the mixture is calcined for 2 hours at 800 ℃ and 35kHz, and the mixture is taken out and naturally cooled to 20 ℃ for standby.
Activated fly ash and water were mixed in an amount of 1g:3mL, ultrasonic treating at 30kHz and 53 deg.C for 1.5h, crystallizing at 103 deg.C for 45h, filtering the crystallized product with Buchner funnel, and drying at 115 deg.C and 65KPa for 13h; and after the drying is finished, passing through a 300-target quasi-test sieve to obtain the NaP type molecular sieve.
In this example, the yield of the fly ash-based NaP-type molecular sieve was 87.6%, and CO was adsorbed 2 Can be up to 116.8cm 3 /g。
As can be seen from the above examples, the present invention provides a method for preparing a fly ash-based NaP-type molecular sieve. The method comprises the steps of mixing fly ash with acid liquor for acid washing to obtain acid-washed fly ash; mixing the acid-washed fly ash, sodium hydroxide and water, and then activating by utilizing microwave radiation, and fully carrying out a melting reaction at high temperature to convert the silicon aluminum mineral substances which are not easy to dissolve into aluminosilicate; then accelerating the intense movement of molecules under the cavitation of ultrasound, pre-crystallizing by using the ultrasound, shortening the time of inducing nucleation, fully carrying out the internal reaction of the mixed solution,increasing mass transfer rate and accelerating the formation of more soluble and very tiny silica-alumina gel particles, thereby obtaining the fly ash-based NaP type molecular sieve with high purity and uniform particle size, and the adsorption capacity of carbon dioxide can reach 118cm 3 And/g, has excellent properties.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
Claims (9)
1. The preparation method of the fly ash-based NaP type molecular sieve is characterized by comprising the following steps of:
(1) Mixing the fly ash with acid liquor and drying to obtain acid-washed fly ash;
(2) Mixing the acid-washed fly ash, sodium hydroxide and water, and then calcining by microwaves to obtain activated fly ash;
(3) Mixing activated fly ash with water, and sequentially carrying out ultrasonic treatment, crystallization and drying to obtain the fly ash-based NaP molecular sieve;
the mass volume ratio of the activated fly ash to the water in the step (3) is 1g: 2-4 mL;
the ultrasonic frequency in the step (3) is 30-35 kHz, the temperature is 50-60 ℃ and the time is 1-4 h.
2. The preparation method according to claim 1, wherein the acid solution in the step (1) is a hydrochloric acid solution or a nitric acid solution, and the concentration of the acid solution is 1-3 mol/L;
the mass ratio of the fly ash to the acid liquid is 1:2 to 6.
3. The preparation method according to claim 1 or 2, wherein the stirring speed of the mixing in the step (1) is 50 to 100rpm, the stirring time is 24 to 26 hours, and the stirring temperature is 20 to 30 ℃;
the temperature of the drying in the step (1) is 100-110 ℃ and the time is 12-13 h.
4. A method according to claim 3, wherein the mass ratio of the acid-washed fly ash to sodium hydroxide in step (2) is 1:0.5 to 2;
the concentration of sodium hydroxide in the mixture of the acid-washed fly ash, sodium hydroxide and water is 1.25-3.75 mol/L.
5. The method according to claim 2 or 4, wherein the microwave calcination in step (2) is carried out at a temperature of 700 to 800 ℃ for a time of 1 to 2 hours and a frequency of 30 to 35kHz.
6. The process according to claim 1, 2 or 4, wherein the crystallization in step (3) is carried out at a temperature of 100 to 110℃for a period of 12 to 48 hours.
7. The method according to claim 6, wherein the drying temperature in the step (3) is 105 to 115 ℃, the vacuum degree is-40 to-80 kPa, and the time is 12 to 13 hours.
8. The fly ash-based NaP-type molecular sieve obtained by the preparation method of any one of claims 1 to 7.
9. The use of the fly ash based NaP-type molecular sieve of claim 8 in carbon dioxide adsorption.
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| CN107381524A (en) * | 2017-08-15 | 2017-11-24 | 中国神华能源股份有限公司 | The method and NaP molecular sieves of NaP molecular sieves are prepared using white clay as raw material |
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